A December 2018 study in the American Academy of Pediatrics found a large percentage of developmentally normal, healthy babies do not reach the milestone of sleeping through the night by age six months or even one year.
For the study, “Uninterrupted Infant Sleep, Development, and Maternal Mood,” Canadian researchers analyzed information from the Maternal Adversity, Vulnerability, and Neurodevelopment longitudinal birth cohort study, which recruited participants from obstetric clinics in Montreal, Québec and Hamilton, Ontario. Sleeping through the night was defined as either six or eight hours of sleep without waking up. Sleep measures were available for 388 infants at six months old, and 369 infants at a year old.
At six months of age, according to mothers’ reports, 38 percent of typically developing infants were not yet sleeping at least six consecutive hours at night; more than half (57 percent) weren’t sleeping eight hours. At 12 months old, 28 percent of infants weren’t yet sleeping six hours straight at night, and 43 percent weren’t staying asleep for eight hours.
Researchers also examined whether infants who woke up at night were more likely to have problems with cognitive, language or motor development; they found no association. They also found no correlation between infants waking up at night and their mothers’ postnatal mood.
— Source: aap.org